Bidirectional EVSE Battery Recalibration for Accurate Range Estimates
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Solution Overview
Problem
Traction battery electric charge capacity values become inaccurate over time, leading to unreliable estimates of vehicle driving range and battery health, as the battery degrades and only a small fraction of its capacity is utilized during short commutes, necessitating a method to improve accuracy and reduce recalibration costs.
Innovation Solution
An electric energy storage device management system (EESDMS) that exchanges data with electric vehicle supply equipment (EVSE) to select and control charging and discharging schedules, optimizing the depth of discharge and recalibration processes to enhance capacity estimates and reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the traction battery is used for short commutes where only a small fraction of capacity is utilized, then the battery operates within a limited capacity range, but the charge capacity value becomes inaccurate over time due to insufficient full discharge cycles
Solution Approach 1:
The system performs preliminary calibration actions by scheduling bidirectional power transfer sessions that deliberately discharge the battery to various states including full discharge, then recharge it. This preliminary full-cycle operation establishes accurate capacity baseline values before normal short-commute usage begins, ensuring measurement precision is maintained despite limited operational depth
Solution Approach 2:
The system changes the operational parameters by transitioning from normal short-commute discharge patterns to extended bidirectional power transfer sessions with different discharge depths (30%, 60%, 90%, 100%). These parameter changes enable comprehensive capacity mapping across the full operating range, resolving the inaccuracy caused by limited usage patterns
2Measurement precision
If bidirectional power transfer is used to recalibrate charge capacity values through full discharge and recharge cycles, then charge capacity value accuracy improves, but the time and energy required for recalibration increases
Solution Approach 1:
The system applies partial action by offering multiple calibration session types with different discharge depths (30%, 60%, 90%, 100%). Users can select partial discharge sessions (30-60%) for quick recalibration when time is limited, or excessive action with full discharge (100%) when maximum accuracy is needed. This resolves the contradiction by providing time-efficient partial calibration options while maintaining the ability to perform comprehensive full calibrations
Solution Approach 2:
The system implements periodic calibration sessions scheduled at intervals rather than requiring continuous or frequent full discharges. The bidirectional power transfer system can perform calibration cycles periodically (e.g., weekly or monthly), maintaining accuracy over time without requiring constant time investment. This periodic approach balances the need for ongoing calibration with time constraints
3Adaptability or versatility
If the traction battery capacity is large but only a small fraction is utilized during short commutes, then the battery serves daily needs effectively, but the unutilized capacity remains uncalibrated leading to inaccurate state of charge estimates
Solution Approach 1:
The bidirectional power transfer system provides multi-functionality by serving both the vehicle's propulsion needs and the calibration function. During scheduled sessions, the same battery that powers daily commutes is also discharged to various states and recharged through the EVSE, simultaneously performing energy storage and capacity characterization. This universal approach eliminates the need for separate calibration equipment while maintaining daily operational adaptability
Solution Approach 2:
The EVSE (Electric Vehicle Supply Equipment) acts as an intermediary that enables the battery to access its full capacity range. The EVSE provides controlled charging during bidirectional power transfer sessions, allowing the battery to be charged to various states (30%, 60%, 90%, 100%) after discharge. This intermediary facilitates comprehensive calibration of the entire capacity range without requiring the vehicle to operate in modes that would deplete the battery during normal use
Data Source
AI summary
Methods and system are described for recalibrating a charge storage capacity value of an electric energy storage device. In one example, the charge electric energy storage device may be a battery. The charge storage capacity value may be recalibrated via discharging and charging a battery via electric vehicle supply equipment.